The present invention concerns trash removal apparatuses (devices for eliminating impurities) for application in fiber cleaning aggregates of a spinning mill and corresponding aggregates.
In principle, it is known that trash removal apparatuses equipped with "knives" or "blades" are provided on cards as well as on (fiber flock) cleaning machines. In a conventional fiber flock cleaner, the material fed normally is supplied in the form of a lap or batt and the cleaned material is transferred (pneumatically) to the next machine in the blowroom line. In the card, the trash removal apparatus acts on fiber material presented in the form of a web, the degree of opening of the fiber material being much higher than of the fibers in fiber flocks. In the flock cleaner the material still has a certain degree of cohesion, which on the card has disappeared or, at least, is much lower.
The present invention deals with trash removal apparatuses or fiber cleaning aggregates respectively, for the flock cleaning stage, at which the material to be cleaned has not yet been opened down to the individual fiber, as well as for the card where the material is presented in the form of a web consisting of fiber material opened down to the individual fiber. The present invention is laid out specifically for application in a new cleaning module according to EP-A-810 309 in which this module is arranged in a card feed chute. The present invention also could be applied, however, in an otherwise conventional flock cleaner or on a card.
A typical conventional trash removal device applied on a card is explained in the following with reference to the FIG. 1 and thus a discussion of the state of the art can be dispensed with here.
Flock cleaners with adjustable eliminating elements are shown in the following documents:
DE-A-27 12 650: proposes a cleaner with a plurality of rolls each of which is provided with a housing containing an elimination opening. Each elimination opening is coordinated to a separating edge and the separating edges are adjustably mounted to housing parts. The manner in which the adjustment is effected is not mentioned in DE-A-27 12 650.
EP-A-481 302: concerns an adjustable grid arrangement. The FIGS. 5 and 6 and the corresponding description reveal in detail the manner in which the adjustment of certain grid elements is effected. These Figures are also shown in the present application and a more detailed description thus can be dispensed with here.
EP-A-459 465: an essentially conventional cleaning device with separating knives is provided in which the knives, arranged in the upstream vicinity of the material outlet, are complemented with an adjustable separating surface.
U.S. Pat. No. 5,031,279: individually adjustable elements are provided on a common support member. The knives are to be set extending in substantially radial direction relative to a roll.
U.S. Pat. No. 4,805,268: a motor driven actuating device is provided for various adjustable elements. In this case, the radial setting of a knife as a whole, as well as the pivoting about an axle that coincides with the knife edge, are provided. In a further embodiment, a guide element is adjustable, but the separating knives are arranged fixedly. Suction devices are mentioned in these documents, but none of them is shown in the corresponding Figures (FIG. 3 and FIG. 6).
In the state of the art, frequently "knives" are referred to as "blades". A "knife" usually comprises a blade, which can be adjusted relative to a rotating roll or drum. It is known also that a similar function can be effected by an edge, also referred to as "separating" or "eliminating" edge. This edge is formed by an element not necessarily designed as an adjustable "knife" but, for example, as a "grid bar". The present invention is applicable also in arrangements of this type. In order to avoid cumbersome repetitions in the description, the term separating element with an edge is to be understood to comprise the particular forms of a bar, knife or blade, respectively.
A fiber processing machine is known with a rotating roll or drum in which arrangement a fiber/air stream flows in a "working gap" provided between the circumference of the roll and a cover surrounding it. A separating element is provided in the cover. Separation selectivity is achieved in that the roll is provided with a clothing holding the fibers whereas trash particles, mostly heavier than the fibers, are shoved radially outward towards the cover where they can be deflected from the stream with the help of the separating element. The working gap generally extends substantially across the whole axial length (across the "working width") of the roll.
In a machine of this type, it is known at least from EP-A-481 302 and U.S. Pat. No. 4,805,268 that the angular position of a separating element is adjusted relative to the stream of material in order to influence the separating effect.
The present invention can be combined with the invention (the "earlier invention") according to EP-A-848 091 (the "earlier application").
The goal of the earlier invention is the improvement of the air flow management downstream from a separating element provided with a suction device. In an arrangement of this type, the nep formation induced by air turbulences in a fiber processing machine can be reduced. An improvement of the trash separation as such, however, also can be achieved.
Thus, the earlier invention thus provides a fiber processing machine with a separating element in which the fibers as well as the air are guided in a generally predetermined transporting direction past the element. Trash particles are then selectively eliminated from the fiber/air stream with the help of the element. The invention is characterized in that at least one measure is taken for influencing the air stream conditions in the zone downstream from the element. Said measure can be taken in such a manner that air turbulences downstream in the transporting direction from the element are limited or even eliminated.
The measure preferably consists in that the air eliminated via the element is at least partially replaced by freshly supplied air. The freshly supplied air expediently flows into the zone adjoining the element downstream, preferentially within a distance of less than 20 mm.
Preferentially, the arrangement is self-adjusting as to the inflowing air quantity, so that no application of blowing air is required. If the free flow cross-section area of the air inlet duct is chosen sufficiently large, then the required air stream is generated owing to a vacuum or below atmospheric pressure prevailing in the room downstream from the element.
The present invention advantageously can be applied in a module according to the Swiss patent application No. CH 1819/97 filed Jul. 30 1997. A module of this type comprises a transporting roll for a fiber/air stream and a plurality of trash eliminating devices distributed along the circumference of the roll in which each device comprises a separating element, an eliminating gap, and trash elimination device coordinated with the gap.